On the location of a silage pit, if I've understood the site correctly, it is on the opposite side of the road from the fields, and largely opposite trees, rather than fields (at least today).
So it wouldn't be the most convenient location for storing material taken from the fields. That doesn't necessarily mean it was erected for suspicious reasons. Possibly it was just the nearest site that the farmer could use - e.g. didn't want to compromise growing space in the field itself, and thought that worth the hassle of moving material across the road.